<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <script src="js/jquery-3.3.1.min.js"></script>
</head>
<body>
    <div id="d1">aaa</div>
    <p class="hello">bbb</p>
    <span class="hello">ccc</span>
    <div>
        <span>ddd</span>
    </div>
    <div>
        <p>
            <span>eee</span>
        </p>
    </div>

    <script>
        $('#d1').css('color','#f00')

        $('.hello').css('color','#00f').css('background','pink') // 隐式迭代、链式写法

        console.log($('p').text())

        $('div > span').css('font-size','30px')
    </script>
</body>
</html>